Display apparatus

ABSTRACT

There is a demand for preventing display quality of a display apparatus from deteriorating. When charged particles ( 9 ) are attracted to a first electrode ( 3 ), the distribution density may not become uniform over the entire area A 1  and only the distribution density in the periphery of the first electrode ( 3 ) (see reference numeral A 3 ) may be locally reduced. The present invention places a colored layer ( 5 ) having the same color as the color of charged particles in this area A 3 . Therefore, even if the distribution density is low, the low density is hardly visually recognized, making it possible to prevent the display quality from deteriorating.

TECHNICAL FIELD

The present invention relates to a moving particle type displayapparatus which performs a display based on charged particles which movewhen a voltage is applied thereto.

BACKGROUND ART

Development and research into moving particle type display apparatuseswhich perform a display based on charged particles which move when avoltage is applied thereto is being carried forward vigorously in recentyears, and great attention is focused above all on an electrophoresisdisplay apparatus.

This type of electrophoresis display apparatus is provided with a backsubstrate and a front substrate arranged with a predetermined gap inbetween and an insulating liquid and charged particles are placed in thegap between these substrates. Furthermore, each pixel is provided with afirst electrode having a large display area and a second electrodehaving a small display area on one substrate (back substrate). Forexample, when a monochrome display is performed, a color difference isused for a display as follows:

-   (1) When charged particles are attracted to the first electrode and    scattered over a wide area, the first electrode is covered with the    charged particles, and therefore the color (e.g., black) of the    charged particles is visible to an observer.-   (2) When charged particles are attracted to the second electrode and    concentrated in a narrow area, the color (e.g., white) of the area    where the first electrode is formed is visible to the observer.

There is also a proposal on a display apparatus constructed in such away that a shielding layer is placed to hide the second electrode andcharged particles attracted by the second electrode are not visible tothe observer (Japanese Patent Application Laid-Open No. H09-211499).

However, the above described electrophoresis display apparatus hasproblems yet to be solved in aspects of display quality. This seems tobe attributable to the following two factors:

First, in the case (1) above, it is desirable that charged particles bescattered over the entire first electrode at substantially the samedensity and the first electrode be hidden behind the charged particles.However, in reality, the density of the charged particles is reduced inareas adjacent to the second electrode and the “color of the base (thatis, the color of the area where the first electrode is formed)” isreflected and made visible. For this reason, the display qualitydeteriorates. The reasons for such a phenomenon are not clearly definedbut there are a few possible reasons as follows:

-   1) Since the second electrode has the same polarity as that of the    charged particles, an electrostatic repulsive force may be generated    between the second electrode and charged particles.-   2) When a barrier is placed so as to separate a pixel, this causes    the “area where the second electrode is formed” and areas adjacent    thereto not to become level but inclined and as a result, the    charged particles may be hardly at rest.

DISCLOSURE OF THE INVENTION

The present invention has been implemented in view of the abovedescribed circumstances and it is an object of the present invention toprovide a reflective display apparatus which creates a display by movingparticles, comprising a front substrate and a back substrate, aplurality of charged particles sandwiched between the front substrateand back substrate, a first electrode and a second electrode placed onthe back substrate, a support member provided to keep a distance betweenthe front substrate and the back substrate and a colored area on theback substrate, characterized in that reflecting means is provided inthe space partitioned by the support member and the colored area isplaced in such a way that the surface of projection on the backsubstrate of the second electrode and the surface of projection on theback substrate of the colored zone at least contact with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are cross-sectional views showing an example of astructure of an electrophoresis display apparatus according to thepresent invention;

FIG. 2 is a cross-sectional view showing another example of thestructure of the electrophoresis display apparatus according to thepresent invention;

FIG. 3 is a cross-sectional view showing a further example of thestructure of the electrophoresis display apparatus according to thepresent invention;

FIGS. 4A and 4B are cross-sectional views showing a still furtherexample of the structure of the electrophoresis display apparatusaccording to the present invention;

FIGS. 5A and 5B are cross-sectional views showing a still furtherexample of the structure of the electrophoresis display apparatusaccording to the present invention; and

FIG. 6 is a cross-sectional view showing a still further example of thestructure of the electrophoresis display apparatus according to thepresent invention.

FIG. 7 is a cross-sectional view showing a still further example of thestructure of the electrophoresis display apparatus according to thepresent invention.

BEST MODE FOR CARRYING OUT THE INVENTION

For the purpose of explaining embodiments of the present invention, thefollowing terms, etc., will be defined. The color of the surfaces ofcharged particles is defined as a “first color.” The range in whichcharged particles can exist is defined as one “pixel.” When the area ofa portion involving the display performance of the apparatus isdiscussed, this area is defined as the area of an image obtained byvertically projecting the portion onto a plane parallel to thesubstrate. When this should be specifically clarified, a term “projectedarea” is used.

With reference now to FIGS. 1A and 1B to FIG. 3, an embodiment of thepresent invention will be explained below.

An electrophoresis display apparatus according to this embodimentincludes a back substrate 1 and a front substrate 2 and an insulatingliquid 8 and a plurality of charged particles 9 are placed between thesubstrates 1 and 2. For each pixel A, a first electrode 3 and a secondelectrode 4 are placed. The first electrode is placed along the backsubstrate in a relatively wide area (hereinafter referred to as “firstelectrode area”) A₁ and the second electrode is placed in a relativelynarrow area (hereinafter referred to as “second electrode area”) A₂.When both the first electrode area and the second electrode area bordereach other on a boundary, a colored area A₃ colored in substantially thesame color as the first color is made up of both areas adjacent to theboundary and when the first electrode area and the second electrode areado not directly border each other and there is an area between the twoareas (hereinafter referred to as “intermediate area”), the colored areaA₃ is made up of the intermediate area and areas adjacent to theintermediate area. Therefore, when the width of the second electrodebetween the first electrode areas is small, the entire second electrodearea may be included in the colored area as shown in FIG. 1A, FIG. 1B,FIG. 2 and FIG. 3. The first electrode area except the colored area iscolored in a different color (hereinafter referred to as “secondcolor”). The colored area A₃ is preferably strip-shaped along theboundary between the first electrode and second electrode.

When the colored area A₃ is too wide, the part displaying the secondcolor, that is, the proportion of the part of the first electrode areaA₁ other than the colored area is reduced, causing visibility to bereduced when the second color is displayed. On the contrary, when thecolored area A₃ is too narrow, the same problem as that of theconventional art occurs, that is, when the first color is displayed,loss of color may occur. The area of the colored area A₃ needs to bedecided taking all these problems into consideration. More specifically,it is necessary to design the area and shape of the colored area A₃taking into account an area C (hereinafter referred to as “particlehiding area”) of the first electrode area hidden behind chargedparticles when the charged particles are concentrated in the vicinity ofthe second electrode and an area E where the first electrode area isexposed because of an insufficient density of the charged particles(hereinafter referred to as “exposed area of the first area”) when thecharged particles are moved onto the first electrode.

First Embodiment

With reference to FIGS. 1A and 1B to FIG. 3, a first embodiment of thepresent invention will be explained below.

It is possible to place a support member 6 between substrates 1 and 2 soas to partition a pixel. In that case, a second electrode 4 may beplaced:

-   (1) between the support member 6 and a back substrate 1 as shown in    FIG. 1A and FIG. 2,-   (2) on the side of the support member 6 as shown in FIG. 1B or-   (3) at a position other than the position at which the support    member 6 is placed as shown in FIG. 3.

In order to calculate the particle hiding area in the modes (1) to (3),it is possible to calculate the projected area of the group of chargedparticles concentrated in the vicinity of the second electrode from thepixel shape and diameter of charged particles and calculate theprojected area based on this calculation result. When charged particles9 cannot be accumulated on the surface of the second electrode 4parallel to the back substrate as in the cases of the mode (1) in FIG.1A and FIG. 2 above and the mode (2) in FIG. 1B, it is possible tocalculate the particle hiding area from the projected area of the groupof charged particles concentrated in the vicinity of the secondelectrode. When the charged particles 9 can be accumulated on thesurface of the second electrode 4 parallel to the back substrate as inthe case of the mode (3) above in FIG. 3, it is possible to calculatethe particle hiding area by subtracting the area of the second electrodearea on which charged particles are placed from the projected area ofthe group of charged particles concentrated in the vicinity of thesecond electrode.

In order to decide the value of the particle hiding area and the shapemore accurately, it is possible to carry out a field intensitysimulation and decide the particle hiding area and the shape along anequipotential line when a voltage of the same polarity as that ofcharged particles is applied to the first electrode 3 or based on theresult of an optical observation when charged particles are concentratedaround the second electrode.

With regard to the value of the exposed area of the first area and theshape, it is possible to carry out a field intensity simulation anddecide the exposed area of the first area and the shape along anequipotential line when a voltage of the polarity opposite to that ofcharged particles is applied to the first electrode 3. Or it is alsopossible to decide the exposed area of the first area and the shapebased on the result of an optical observation when particles are movedonto the first electrode and calculate the exposed area of the firstarea and the shape according to the actual situation.

When the particle hiding area including the shape exceeds the exposedarea of the first area, it is preferable to define the intermediate areaand shape for the colored area A₃. In that case, the colored area A₃need not necessarily cover the entire width of accumulated chargedparticles.

On the other hand, when the particle hiding area is smaller than theexposed area of the first area, it is necessary to decide the area ofthe colored area and the shape according to the priority level of lightand shade, but from the standpoint of a pixel aperture ratio, it isdesirable to set the area and the shape of the colored area to theparticle hiding area or smaller.

A display is performed by applying a voltage between the secondelectrode 3 and first electrode 3 and thereby moving charged particles 9between the two electrodes. For example, when the charged particles 9are attracted to the first electrode 3 and placed so as to cover thefirst electrode 3, the first color of the charged particles 9 isvisually recognized as the color of the pixel. On the other hand, whenthe charged particles 9 are attracted to the second electrode 4, thefirst electrode area A₁ is exposed and the second color is visuallyrecognized as the color of the pixel.

Note that there are various methods for coloring the first electrodearea A₁ such as a method of coloring the first electrode itself, amethod of providing a colored layer in addition to the electrode and amethod of coloring an insulating layer placed so as to cover the firstelectrode.

Furthermore, as the method of coloring the colored area A₃, a method ofplacing a colored layer (see reference numeral 8 in FIGS. 1A and 1B)colored in substantially the same color as the first color is available.As the method of forming such a colored layer, a method of applying aphotosensitive resin layer mixed with pigment and dye, then carrying outexposure and wet developing or a method of forming the colored layerusing a printing method is available.

Hereinafter, components of the electrophoresis display apparatus will beexplained.

It is preferable to place the support member 6 in the gap betweensubstrates so as to partition one pixel from another. It is possible touse polymer resin as this support member 6 and more specifically, it ispossible to use polyimide resin, polyester resin, polyacrylate resin,polymethacrylate resin, polycarbonate resin, polyallylate resin, novolacresin, epoxy resin, etc., as this support member 6. Examples of themethod of forming this support member 6 include:

-   Method of applying a photosensitive resin layer, then carrying out    exposure and wet developing-   Method of forming support member 6 using a printing method-   Method of forming a barrier and then adhering it to the substrate-   Method of forming support member 6 on an optically transparent    substrate surface through molding

For the substrate 1 and 2, it is possible to use a polymer film such aspolyethylene terephthalate (PET), polyether sulfone (PES), polyimide(PI) and polyethylene naphthalate (PEN), polycarbonate (PC), aninorganic material such as glass and quartz or a stainless steelsubstrate, the surface of which includes an insulating layer. Note thatfor the substrate 2 on the observer side, it is possible to use amaterial with high transmittance of visible light such as a transparentpolymer film and glass. Furthermore, it is also possible to form a resinlayer (see reference numeral 42) made of a polymer material whose rubberhardness is within a range of 10 to 90, or more specifically siliconresin, natural rubber, thermoplastic elastomer resin on the surface ofthe substrate 2 (surface contacting the insulating liquid 8).

Furthermore, it is possible to use any material for the electrodes 1 and2 if it is at least a conductive material that can be patterned, forexample, indium tin oxide (ITO), aluminum and titanium. Note that in theelectrophoresis display apparatus shown in FIGS. 1A and 1B, the firstelectrode 3 and second electrode 4 are formed at different heights (thatis, a position offset with respect to the direction normal to thesubstrate), but they can also be formed at the same height. Furthermore,in the electrophoresis display apparatus shown in FIGS. 1A and 1B, thefirst electrodes 3 of different pixels are separated from one anotherand there is no electrical continuity among them, but it is alsopossible to provide electrical continuity among the first electrodes 3of different pixels.

It is preferable to form an insulating layer on the surfaces of theseelectrodes to

-   insulate one electrode from another or-   prevent injection of charges from electrode to charged particles 9.

As a material used for this insulating layer, it is preferable to use athin film in which pinholes are hardly formed. More specifically,polyimide resin, polyester resin, polyacrylate resin, polymethacrylateresin, polycarbonate resin, etc., having high transparency can be used.

Furthermore, it is also possible to:

-   place a scattering layer in front of the first electrode 3 (upper    part in the figure) (see reference numeral 10) or-   make the first electrode 3 transparent and place a reflecting layer    behind (lower part in the figure) (not shown).

As the scattering layer, it is possible to use a transparent insulatinglayer containing highly reflective micro particles and it is preferableto use titanium oxide or Al₂O₃ as micro particles and acrylic resin,urethane resin, fluorine-based resin, norbornene resin, PC, PET, etc.,can be used as the insulating resin. When the scattering layer is thick,it is possible to increase the reflective factor and improve the displayquality, but on the contrary it is possible to cause the drive voltageto rise. Therefore, the thickness of the scattering layer is preferablywithin a range of 0.1 to 20 μm.

An average particle diameter of charged particles 9 used in the presentinvention is preferably within a range of 0.1 μm or above and 10 μm orbelow. The coloring agent is not particularly limited, but it can be,for example, carbon black, titanium oxide, barium sulfate, nigrosine,iron black, aniline blue, calcoil blue, chrome yellow, ultramarine blue,Du Pont oil red, quinoline yellow, methylene blue chloride,phthalocyanine blue, phthalocyanine green, sky blue, rhodamine lake,etc. Furthermore, as particle resin, polystyrene, polyethylene,polyester, polymethacrylate, polyacrylate, polyacrylic ester,polyethylene-based resin such as polyethylene-acrylic acid copolymer,polyethylene-methacrylic acid copolymer, polyethylene-vinyl acetatecopolymer, other polymer material such as polyvinyl chloride resin,nitrocellulose, phenol resin, and polyamide resin can be used. Thesematerials can be used singly or with two or more types combined.

As the insulating liquid 8, it is preferable to use a low-conductive,high-insulating organic solvent. Such a solvent can be aromatichydrocarbon-based solvent such as benzene, toluene and xylene, aliphatichydrocarbon-based solvent such as hexane, cyclohexane, paraffin-basedhydrocarbon solvent, isoparaffin-based hydrocarbon and naphthene-basedhydrocarbon, hydrocarbon halide-based solvent or silicon oil, highpurity petroleum, etc., but above all, aliphatic hydrocarbon solvent ispreferably used and more specifically, isopar-G, H, M, L (manufacturedby Exxon Chemical), Shellsol (Showa Shell Japan), IP Solvent 1016, 1620,2028, 2835 (Idemitsu Petrochemical), etc., can be used. These can beused singly or with two or more types combined.

The insulating liquid 8 may also contain additives such as chargecontrol agent, dissociation stabilizer, scattering stabilizer for thepurposes of increasing the amount of charge of charged particles orproviding charge stability.

As the charge control agent, it is preferable to use metallic soap andmore specifically, metallic soap such as cobalt naphthenate, zirconiumnaphthenate, copper naphthenate, iron naphthenate, lead naphthenate,manganese naphthenate, zinc naphthenate, cobalt octanate, zirconiumoctanate, iron octanate, lead octanate, nickel octanate, manganeseoctanate and zinc octanate can be used but the charge control agent isnot limited to them.

Furthermore, rosin ester or rosin derivative can be used for thepurposes of increasing the amount of charge of charged particles orproviding charge stability. Rosin ester or rosin derivative is notparticularly limited as far as it is soluble to the insulating liquid,but can be, for example, gum rosin, wood rosin, tallol rosin, rosindenatured maleic acid, rosin denatured pentaerythritol, rosin glycerinester, partially hydrogen added rosin methyl ester, partially hydrogenadded rosin glycerin ester, partially hydrogen added rosin triethyleneglycol ester, fully hydrogen added rosin pentaerythritol ester, maleicacid denatured rosin ester, fumaric acid denatured rosin ester, acrylicacid denatured rosin ester, maleic acid denatured rosin pentaerythritolester, fumaric acid denatured rosin pentaerythritol ester, acrylic aciddenatured rosin glycerin ester, maleic acid denatured rosin glycerinester, fumaric acid denatured rosin glycerin ester and acrylic aciddenatured rosin glycerin ester.

Specific examples of the scattering stabilizer include polybutadiene,polyisoprene, polyisobutylene, polybutene, styrene butadiene copolymer,styrene isoprene copolymer, styrene maleic anhydride copolymer,norbornene resin and polyethylene wax. Above all, styrene butadienecopolymer is preferable, for example, as commercially availablematerials, E-SBR, S-SBR (manufactured by JSR Corporation), NIPOL 1502,NIPOL 1712, NIPOL NS112, NIPOL NS116, NIPOL 1006, NIPOL 1009(manufactured by Zeon Corporation), TAFDENE, TUFPRENE, Asaprene(manufactured by Asahi Kasei Chemical Corporation), Sumitomo SBR(manufactured by Sumitomo Chemical Co., Ltd.), etc., can be used.

In the present invention, these charge control agents, chargestabilizers and scattering stabilizers can be used singly or with two ormore types combined.

Then, the effects of this embodiment will be explained.

According to this embodiment, of the first electrode area A₁, the areaA₃ adjacent to the second electrode 4 is colored in substantially thesame color as the color of the charged particles 9 (first color).Therefore, when the charged particles 9 are attracted to the firstelectrode 3, even if the density of the charged particles in the area A₃is lower (than the density of the charged particles in the rest of thefirst electrode area A₁), the color seen from the gaps of chargedparticles is simply substantially the same color as the first color andthe low density of charged particles is hardly visually recognized,which prevents the display quality from deteriorating.

Second Embodiment

With reference to FIGS. 4A, 4B, 5A and 5B, another embodiment of thepresent invention will be explained below.

An electrophoresis display apparatus according to this embodiment isprovided, as shown in FIGS. 4A and 4B, with a back substrate 1 and atransparent front substrate 2 arranged with a certain spacing inbetween, a support member 6 placed so as to keep the spacing between thesubstrates constant, a transparent insulating liquid 8 placed in a spacesurrounded by the back substrate 1, front substrate 2 and support member6, a plurality of colored charged particles 39 scattered in theinsulating liquid, a colored first electrode 3 formed on the backsubstrate 1, a second electrode 4 colored differently from the firstelectrode, a transparent insulating layer 41 placed on the firstelectrode 3 and second electrode 4 and a colored layer 35 placed on theback substrate 1. This colored layer 35 is placed in a gap between thefirst electrode 3 and second electrode 4 in a pixel.

Note that it is important that the colored layer 35 be placed so as toinclude at least the gap between the first electrode 3 and secondelectrode 4. However, the colored layer 35 shown in FIGS. 4A and 4B doesnot limit the position and shape thereof. In addition to the positionshown in FIGS. 4A and 4B, it is also possible to place the colored layer35 on the same plane as those of the first electrode 3 and secondelectrode 4 as shown in FIG. 5A or place the colored layer 35 on theplane including the first electrode 3 and second electrode 4 using whitecharged particles to display a white color and the color of the coloredlayer as shown in FIG. 5B. As preferred modes of this colored layer 35,it is preferable to place it so as to have a greater width than the gapbetween the first electrode 3 and second electrode 4, place it so as toinclude the plane overlapping the support member 6 within a planehorizontal to the back substrate 1 or form a film integral with the backsubstrate 1 so as to eliminate the need for placing it positioned at thegap between the first electrode 3 and second electrode 4 as shown inFIGS. 4A and 4B.

However, it is necessary to set the volume resistivity value so as toprevent the colored layer 35 from constituting an electricallyshort-circuit path between pixels. It is preferable to use a materialfor the colored layer having a volume resistivity value of 1E+6 Ωcm orgreater.

Furthermore, it is necessary to set the color of the colored layer to acolor capable of removing light of a wavelength region, which affectsdisplay contrast or brightness. For example, when the color of thecharged particles 39 is substantially the same as the color of thesecond electrode 4, it is preferable that the color of the secondelectrode 4 be substantially the same as the color of the colored layer35. Furthermore, to completely prevent unnecessary reflected light frombetween the electrodes, the color of the colored layer 35 is preferablyblack.

The case where the color of the first electrode 3 is different from thecolor of the second electrode 4 has been described above, but note thatthis explanation does not limit the colors of the respective electrodes.For example, the second electrode 4 and first electrode 3 may also havethe same color. The colors of these electrodes should be selected anddesigned in consideration of the combination of colors, etc., of thecharged particles 39 and insulating liquid 8 so that optimal brightnessand contrast can be obtained for the display apparatus.

Furthermore, in FIGS. 4A and 4B, only one type of the charged particles39 is described, but two or more types can also be used. For example,there may also be a case where a plurality of types of particles havingdifferent particle diameters or different colors or different amounts ofcharge exist.

Furthermore, the color of the insulating liquid 8 is not limited to atransparent color. Any insulating liquid having nature of allowing lightto transmit may be used and selected arbitrarily depending on itsdisplay color characteristic.

Moreover, the type of the insulating liquid 8 is not limited to one typein the entire display area.

That is, among pixel areas partitioned by the support members 36, theremay be cases where different types of insulating liquid 8 are included.For example, it is also possible to form three consecutive areas as oneset and use RGB or CMY as colors of the insulating liquids that fill thethree areas and repeat this set cyclically in the display area.

Then, a display method for the electrophoresis display apparatus shownin FIGS. 4A and 4B will be explained.

A display is performed by applying a voltage between the secondelectrode 4 and first electrode 3 and moving the charged particles 39between the two electrodes. Here, a case where the first electrode 3 iscolored in a highly reflective color and the second electrode 4 iscolored in black will be explained. As shown in FIG. 4A, it is possibleto concentrate charged particles 39 on the second electrode 4 and allowthe first electrode 3 to reflect the incident light and thereby create apixel in a bright display state. On the other hand, as shown in FIG. 4B,when the charged particles 39 are placed on the first electrode 3 andthe reflective first electrode 3 is thereby covered with the chargedparticles 39. Thus, the incident light is reflected by the coloredcharged particles 39, which causes the color of the charged particles 39to be the color displayed in the pixel. For example, when the chargedparticles 39 are colored in black, the display of the pixel in FIG. 4Bbecomes a black display.

Note that since the colored layer 35 is provided between the firstelectrode 3 and second electrode 4 and below the bottom face of thesupport member 6, it is possible to effectively remove unnecessaryreflected light from those areas. Thus, the image created by combiningthe bright display and black display shown in FIGS. 4A and 4B becomes adisplay with high contrast.

Note that the components of the electrophoresis display apparatusaccording to this embodiment may be the same members as those describedin the first embodiment.

As shown above, the effects of this embodiment include the ability toeffectively prevent reflected light from the gap between the secondelectrode and first electrode, which is one cause of leakage of light,and at the same time the ability to remove leaked light from betweenpixels in this process of forming a colored layer. This makes itpossible to achieve high contrast with a simple structure. Furthermore,as shown in FIGS. 4A and 4B, the structure in which a colored layer isplaced between both electrodes and the back substrate eliminates theneed for fine positioning in manufacturing, which simplifiesmanufacturing. In this way, it is possible to achieve high yield in theprocess of the colored layer.

EXAMPLES

The present invention will be explained in more detail using Examplesbelow.

Example 1

In this example, an electrophoresis display apparatus 51 having thestructure shown in FIGS. 1A and 1B will be created.

That is, a back substrate 1 and front substrate 2 are arranged with apredetermined spacing in between, a support member 6 is placed in thespacing between these substrates 1 and 2 so as to partition a pixel Aand each pixel A is filled with an insulating liquid 8 and chargedparticles 9. Furthermore, each pixel A is provided with a firstelectrode 3 and second electrode 4 as shown in the figure. Then, ascattering layer 10 is formed on the entire substrate so as to cover thefirst electrode 3 and a colored layer 5 is placed in the areas A₂ and A₃so as to cover the second electrode 4. Furthermore, the surfaces of thisscattering layer 10, colored layer 5 and support member 6 are coatedwith a transparent insulating layer 11. Furthermore, a resin layer 42 isformed on the surface of the front substrate 2 and an adhesion layer 12is placed between this front substrate 2 and support member 6.

In the present example, polystyrene particles (average particle diameterof 2.5 μm) colored in black with carbon black (CB, average particlediameter of 80 nm) which is inorganic pigment is used as the chargedparticles 9, the colored layer 5 is also colored in black and the firstelectrode area A₁ (to be precise, the part A₁ which is the firstelectrode area except the area A₃ where the colored layer is placed) isdesigned to appear white through the function of the scattering layer10.

Then, the method of manufacturing the electrophoresis display apparatuswill be explained.

First, an aluminum film is formed to a thickness of 100 nm on thesurface of the glass substrate 1 of 0.7 mm thick, which is thenpatterned to form the first electrode 3. Then, the polyurethane resinlayer (scattering layer) 10 whitened by mixing titanium oxide microparticles is formed so as to cover this first electrode 3. Furthermore,a dark-colored carbonized titanium film is formed in the area A₂,patterned into a linear shape through photolithography and dry etchingto form the second electrode 4. The second electrode 4 has a thicknessof 50 nm and a line width of 12 μm.

Furthermore, the aforementioned colored layer 5 is formed. This coloredlayer 5 is linear-shaped so as to be placed not only in the area A₂where the second electrode 4 is formed but also in the area (seereference numeral A₃) where the first electrode 3 is formed.Furthermore, this colored layer 5 is formed by applying photosensitiveresin (CFPR-BK738S manufactured by Tokyo Ohka Kogyo Co., Ltd.) in whichpigment is scattered to a film thickness of 1 μm using a spinner andpatterning it through exposure and wet developing. This colored layer 5has a width of 22 μm and the area A₃ has a width of 5 μm.

Then, by applying photosensitive epoxy resin (SU8 manufactured byMacDermid, Incorporated) followed by exposure and wet developing, thesupport member 6 is formed in the area A₂ where the second electrode 4is formed. The support member 6 has a height of 30 μm, width of 12 μmand spacing of 120 μm. Then, the transparent resin layer 11 made ofpolyacrylate resin (optomer SS6699 manufactured by JSR Corporation) isformed so as to cover the inner surface of the cell.

Then, the UV-cured adhesion layer 12 is formed on the top surface(surface to which the substrate 2 is pasted) of the support member 6.

Then, the concave section partitioned by the support member 6 is filledwith a scattering liquid mixed with charged particles 9. The scatteringliquid is prepared by mixing the charged particles of 1 weight ratio,isopar-H (manufactured by Exxon Corporation) of 100 weight ratio whichis an aliphatic hydrocarbon solvent, zirconium octanate (Nikka octicszirconium, manufactured by Nihon Kagaku Sangyo Co., Ltd.) of 0.1 weightratio, rosin ester (NEOTALL 125H, manufactured by Harima Chemicals,Inc.) of 2.5 weight ratio and styrene butadiene copolymer (Asaprene1205, manufactured by Asahi Kasei Chemicals Corporation) of 0.8 weightratio and stirring it for one hour. Note that the charged polarity ofthe charged particles is negative.

Finally, the substrate 2 made of a polycarbonate film (100 μm thick) isadhered to the support member 6 and UV-cured to create theelectrophoresis display apparatus of the present invention.

Then, the display condition of the present example will be explained.

In the reflective electrophoresis display apparatus 51 created using theabove-described method, when a voltage of the same polarity as thecharged polarity of the charged particles 9 scattered in the insulatingliquid 8 is applied to the first electrode 3, the charged particles 9are attracted to the second electrode 4, which produces a white display.On the contrary, when a voltage of the polarity opposite to the chargedpolarity of the charged particles 9 scattered in the insulating liquid 8is applied to the first electrode 3, the charged particles 9 arescattered over the first electrode 3 and no white patch is found in thearea A₃ and good black brightness is confirmed.

Example 2

In the present example, the electrophoresis display apparatus 51 shownin FIG. 2 will be created. This has a structural difference from theelectrophoresis display apparatus shown in FIGS. 1A and 1B in that thecolored layer 18 is placed only in the area A₃ (without placing it inthe area A₂ where the second electrode 4 is placed) and the rest of thestructure and the manufacturing method are the same.

Then, when the apparatus is driven in the same way as Example 1, thesame display quality can be confirmed.

Example 3

In the present example, the electrophoresis display apparatus 51 shownin FIG. 3 will be created. That is, the second electrode 4 is placed notbetween the support member 6 and the back substrate 1 but outside thearea where the support member 6 is placed and the colored layer 28 isplaced so as to cover the second electrode 4 and stick out toward thefirst electrode 3. Note that the second electrode 4 has a width of 30 μmand the colored layer 28 has a width of 35 μm. The rest of the structureand the manufacturing method are the same as those in Example 1.

When the apparatus is driven in the same way as Example 1, the samedisplay quality can be confirmed.

Example 4

In the present example, the electrophoresis display apparatus shown inFIGS. 4A and 4B will be explained.

Suppose the display apparatus to be created has 200×200 pixels and onepixel is a square of 100 μm per side. Each pixel is surrounded on allfour sides by a transparent support member 6. The support member 6 has aheight of 25 μm and this distance corresponds to the cell gap. Thesupport member 6 has a width of 5 μm and the area occupied by thesupport member 6 within the substrate plane corresponds to thenon-aperture area. Furthermore, a black colored layer 35 is formed as afilm integral with the back substrate within a range of the displayarea. Furthermore, a first electrode 3 and a second electrode 4 areplaced on the colored layer 35 on the back substrate 1 and suppose a gapg (spacing indicated by dotted lines in the figure) between the twoelectrodes is 10 μm. Suppose the area ratio within the pixel of thefirst electrode 3 and second electrode 4 is 7:3. To provide the firstelectrode 3 with a light absorption characteristic, a transparentmaterial is used. That is, light incident on the second electrode 4passes through the transparent second electrode 4 and is absorbed by thecolored layer 35 placed beneath the second electrode 4. On the otherhand, a highly reflective metal is used for the first electrode 3 so asto provide it with a light reflecting characteristic and a fineconcavo-convexo structure is provided on the electrode surface thoughnot shown. This concavo-convexo structure is designed so as to scatterreflected light. Furthermore, in order to prevent charged particles 39and an insulating liquid 8 from provoking electrode reaction or chargeinjection, etc., causing the behavior of the charged particles 39 tochange to substantially an instable condition with time, a transparentthin film insulating layer 41 is laminated on the second electrode 4 andfirst electrode 3. Furthermore, the black charged particles 39 of apredetermined density and transparent insulating liquid 8 are stablyenclosed in a closed space surrounded by the back substrate 1, frontsubstrate 2 and support member 6.

Then, the method of manufacturing the electrophoresis display apparatusaccording to the present example will be explained below.

As the back substrate 1 shown at the bottom in the figure which is asubstrate, a 150 μm PET film is used, a photosensitive resin material(CFPR BK, manufactured by Tokyo Ohka Kogyo Co., Ltd.) containing carbonis applied thereto to a thickness of 3 μm to form the colored layer 35.Then, the black resin material other than the display area is removedusing photolithography. Then, the second electrode 3 is patterned usinga transparent electrode ITO. In the area where the first electrode 3 isplaced, a micro concavo-convexo structure is formed (not shown) usingresin beforehand, the first electrode 3 is patterned thereon using Al toform the reflective first electrode 3. Next, the insulating layer 41 isformed in the display area using transparent acrylic-based resin(optomer, manufactured by JSR Corporation) so as to cover the secondelectrode 4 and first electrode 3. Then, the support member 6 is formedusing a thick film photoresist (THB, manufactured by JSR Corporation)through photolithography. Then, though not shown, polycarbonate resin isapplied to the support member 6 and insulating layer 41 as a thinsurface coating layer. The thickness of the surface coat layer isapproximately 100 nm. Applying this surface coat layer has the effect ofstrengthening the support member 6 with a high aspect ratio againstshock. Then, the space partitioned by the support member 6 on the backsubstrate 1 is filled with the transparent insulating liquid 8 and aplurality of black charged particles 39 in such a way that the densityof charged particles 39 of all pixels becomes uniform. As the insulatingliquid 8, isopar (manufactured by Exxon) is used and black chargedparticles 39 containing carbon having an average particle diameter of 3μm are scattered therein and used. Furthermore, isopar (manufactured byExxon) is used for the insulating liquid 8 and imide succinate isincluded as a charge control agent. After filling, the top end of thesupport member 6 and the front substrate 2 are adhered together and thespace portioned by the support member 6 is sealed with the insulatingliquid 8 and charged particles 39. After the sealing, the frontsubstrate 2 and back substrate 1 are adhered together around thesubstrate using an adhesive (not shown).

Then, the display condition in the present example will be explained.

In the reflective electrophoresis display apparatus 51 created using theabove-described method, when a voltage of the same polarity as thecharged polarity of the charged particles 39 scattered into theinsulating liquid 8 is applied to the first electrode 3, the chargedparticles 39 are attracted to the second electrode 4, producing a brightdisplay. On the contrary, when a voltage of the polarity opposite to thecharged polarity of the charged particles 39 scattered into theinsulating liquid 8 is applied to the first electrode 3, the chargedparticles 39 are attracted to the first electrode 3, producing a blackdisplay, the same black color as the color of the charged particles 39.When a bright display or dark display is performed in this way, thelight leaking from the gap between the first electrode 3 and secondelectrode 4 and from the support member 6 is mostly intercepted by thecolored layer 35, making it possible to obtain a display with highcontrast. Moreover, since this is a process capable of forming thelight-reflecting layer 35 without any control over positioning in anarrow gap of only 10 μm between the first electrode 3 and secondelectrode 4, it is possible to drastically improve yield.

Example 5

In the present example, the electrophoresis display apparatus shown inFIG. 6 will be explained.

Suppose the display apparatus to be created has 200×200 pixels and onepixel is a square of 100 μm per side. Each pixel is surrounded by ablack support member 6. The support member 6 has a height of 10 μm andthis distance corresponds to the cell gap. The support member 6 has awidth of 5 μm.

The gap (g in the figure) between the first electrode 3 and secondelectrode 4 placed on the back substrate 1 is set to 5 μm and thecolored layer 35 having a width (s in the figure) of 20 μm is providedon the back substrate 1 in such a way as to include the gap. Suppose thearea ratio within the pixel of the first electrode 3 and secondelectrode 4 is 7:3. That is, the width s of the colored layer 35 is setsufficiently wide compared to the distance g between the electrodes.This colored layer 35 is patterned by applying a printing method toresin containing carbon. Furthermore, the second electrode 4 and firstelectrode are made of the same material. Furthermore, in order toprevent charged particles 39 and an insulating liquid 8 from provokingelectrode reaction or charge injection, etc., causing the behavior ofthe charged particles 39 to change to substantially an instablecondition with time, a transparent thin film insulating layer 41 islaminated on the first electrode 3 and second electrode 4. Furthermore,a transparent insulating liquid 8 in which white charged particles 39-1and black charged particles 39-2 of a predetermined density arescattered is stably enclosed in a closed space surrounded by the backsubstrate 1, front substrate 2 and support member 6. The white chargedparticles 39-1 and black charged particles 39-2 are charged withdifferent polarities in the insulating liquid 8.

Then, the method of manufacturing the electrophoresis display apparatusaccording to the present example will be explained below.

The colored layer 35 is patterned on the back substrate 1 which is thesubstrate at the bottom in the figure using an SUS substrate having athickness of 0.5 mm and a black resin layer containing carbon thereonaccording to a printing method. The width s of the colored layer at thistime is set to 20 μm. The first electrode 3 and second electrode 4 areformed thereon simultaneously using Al. The gap g between the twoelectrodes is 5 μm and the electrodes are placed so as to besuperimposed on the already formed colored layer 35. Since the width sof the colored layer is sufficiently large compared to the gap g betweenthe electrodes, the positioning process when the first electrode 3 andsecond electrode 4 are patterned is extremely easy. Then, thetransparent insulating layer 41 is coated so as to cover the firstelectrode 3 and second electrode 4. Then, the support member 6 is formedusing photosensitive resin containing carbon around the pixel. Then, thespace partitioned by the support member 6 is filled with the insulatingliquid 8 in which white charged particles 39 and black charged particles39-2 are scattered. Titanium oxide having a particle diameter of 1 to 2μm is used for the white charged particles 39-1 andpolystyrene-polystyrene methacrylate copolymer resin containing carbonblack having a particle diameter of 0.1 to 0.3 μm is used for the blackcharged particles 39-2. Furthermore, isopar (Exxon) is used for theinsulating liquid 8 and imide succinate is included therein as a chargecontrol agent. Then, using the front substrate 2, the closed spacesurrounded by the back substrate 1, front substrate 2 and support member6 is sealed with the insulating liquid 8 in which the white chargedparticles 39-1 and black charged particles 39-2 are scattered.

In the reflective electrophoresis display apparatus 51 created using theabove described method, when a voltage of the same polarity as thecharged polarity of the white charged particles 39-1 scattered into theinsulating liquid 8 is applied to the first electrode 3, the whitecharged particles 39-1 are attracted to the second electrode 4 and theblack charged particles are attracted to the first electrode 3, andtherefore approximately 70% of light incident on the pixel is absorbedby the black charged particles 39-2, producing a dark display. On thecontrary, when a voltage of the polarity opposite to the chargedpolarity of the white charged particles 39-1 scattered in the insulatingliquid 8 is applied to the first electrode 3, the black chargedparticles 39-2 are attracted to the second electrode 4 and the whitecharged particles 39-1 are attracted to the first electrode 3, andtherefore the light incident on the pixel is reflected by the Alelectrode and further scattered by the white charged particles 39-1,thus producing a white bright display.

In this way, unnecessary reflected light which leaks from the gapbetween the first electrode 3 and second electrode 4 can be mostlyintercepted by the colored layer 35, and therefore it is possible toreduce the black reflective factor and obtain a display with highcontrast. Moreover, this is a process capable of forming a lightreflecting layer in a narrow gap of only 5 μm between the firstelectrode 3 and second electrode 4 without any need for difficultpositioning control, and therefore it is possible to drastically improveyield.

Example 6

In the present example, the electrophoresis display apparatus shown inFIG. 7 will be explained.

Suppose the display apparatus to be created has 200×200 pixels and onepixel is a square of 100 μm per side. Each pixel is surrounded by asecond electrode 4 also serving as a support member 6. The secondelectrode 4 has a height of 20 μm and this distance corresponds to thecell gap. Furthermore, the second electrode 4 has a width of 5 μm.

A colored layer 35 is placed on a back substrate 1 and a first electrode3 is connected to a TFT (abbreviation of Thin Film Transistor) which isa switching element 30 through a through hole provided in the centralarea of the pixel. Furthermore, in order to prevent charged particles 39and an insulating liquid 8 from provoking electrode reaction or chargeinjection, etc., causing the behavior of the charged particles 39 tochange to substantially an instable condition with time, an insulatingcolor filter 41 is laminated on the first electrode 3 and secondelectrode 4. Furthermore, a transparent insulating liquid 8 in whichblack charged particles 39 of a predetermined density are scattered isstably enclosed in a closed space surrounded by the back substrate 1,front substrate 2 and support member 6.

Then, the method of manufacturing the electrophoresis display apparatusaccording to the present example will be explained below.

A glass substrate having a thickness of 0.8 mm is used for the backsubstrate 1, which is the lower substrate in the figure and an a-Si TFTis formed thereon. The colored layer 35 is patterned on the a-Si TFTusing photosensitive resin containing carbon. A convex structure isformed on the area peripheral to the pixel and the first electrode 3 andsecond electrode 4 are formed simultaneously using Al. The gap g betweenthe two electrodes is set to 5 μm and the electrodes are superimposed onthe colored layer 35 in which the gap is formed beforehand. Then, thecolor filter, which is the insulating layer 41, is patterned so as tocover the first electrode 3 and second electrode 4. Using three adjacentpixels as one set, a CMY color filter is patterned on the respectivethree pixels. Then, the space partitioned by the second electrode 4,which also serves as the support member, is filled with the insulatingliquid 8 in which black charged particles 39 are scattered.Polystyrene-polystyrene methacrylate copolymer resin containing carbonblack having a particle diameter of 1 to 3 μm is used for the blackcharged particles 39-2. Furthermore, isopar (Exxon) is used for theinsulating liquid 8 and imide succinate is included therein as a chargecontrol agent. Then, using the front substrate 2, the closed spacesurrounded by the back substrate 1, front substrate 2 and firstelectrode 3 which also serves as the support member is sealed with theinsulating liquid 8 in which the black charged particles 3 arescattered.

In the reflective electrophoresis display apparatus 51 created using theabove-described method, when a voltage of the same polarity as thecharged polarity of the charged particles 9 scattered in the insulatingliquid 8 is applied to the first electrode 3, the charged particles 9are attracted to the second electrode 4, producing a bright display. Forexample, when the color filter placed in this pixel is yellow (Y), theyellow color is displayed. On the contrary, when a voltage of thepolarity opposite to the charged polarity of the charged particles 39scattered in the insulating liquid 8 is applied to the first electrode3, the charged particles 39 are attracted to the first electrode 3,producing a dark display in the same black color as the color of thecharged particles.

In this way, unnecessary reflected light which leaks from the gapbetween the first electrode 3 and second electrode 4 can be mostlyintercepted by the colored layer 35, and therefore it is possible toreduce the black reflective factor and obtain a display with highcontrast. Moreover, this is a process capable of forming thelight-reflecting layer 35 in a narrow gap of only 5 μm between the firstelectrode 3 and second electrode 4 without any need for difficultpositioning control, and therefore it is possible to drastically improveyield. Furthermore, it is possible to suppress a mixture of leaked lightfrom the adjacent pixels and thereby provide a bright color display.

As shown above, the moving particle type display apparatus according tothe present invention can prevent unnecessary reflected light fromwithin the pixels. More specifically, of the first electrode area, thearea adjacent to the second electrode is colored in substantially thesame color as the color (first color) of charged particles. Therefore,when the charged particles are attracted to the first electrode, even ifthe density of the charged particles in the area is low (compared to thedensity of charged particles in the rest of the first electrode area),the color seen from the gaps of the charged particles is onlysubstantially the same color as the first color and the low density ofthe charged particles is hardly visually recognized and it is possibleto thereby prevent the display quality from deteriorating. Furthermore,it is possible to suppress leaked light from between the electrodes andthereby improve the display contrast. Furthermore, depending on thedisplay mode, there is no interference of leaked light from the adjacentpixels, which allows a bright display. Furthermore, this colored layercan be placed through a simple process, and therefore it is possible toimprove the yield of manufacturing and reduce cost because there arefewer restrictions on the manufacturing apparatus and materials.

1. A reflective display apparatus that creates a display by movingparticles, comprising: a front substrate and a back substrate; aplurality of charged particles sandwiched between said front substrateand back substrate; a first electrode and a second electrode placed onsaid back substrate; a support member provided to keep a distancebetween said front substrate and back substrate; and a colored areaprovided on said back substrate, wherein reflecting means is provided ina space partitioned by said support member and said colored area isplaced in such a way that the surface of projection on the backsubstrate of said second electrode and the surface of projection on theback substrate of said colored zone at least contact with each other. 2.The reflective display apparatus according to claim 1, wherein saidcolored area is colored in substantially the same color as that of saidcharged particles and the area other than said colored area is coloredin a second color which is different from the color of the chargedparticles.
 3. The reflective display apparatus according to claim 1,wherein said colored area is a light absorbing layer, a gap is providedbetween said first electrode and second electrode within the backsubstrate and the colored area is placed on the back substrate so as tooverlap at least with the gap.
 4. The reflective display apparatusaccording to claim 1, wherein said support member is placed so as topartition the pixel.
 5. The reflective display apparatus according toclaim 1, wherein said second electrode is provided on said supportmember.
 6. The reflective display apparatus according to claim 1,wherein said second electrode is placed between said support member andsaid back substrate.
 7. The reflective display apparatus according toclaim 1, wherein an insulating liquid is further provided in the gapbetween said front substrate and back substrate.
 8. The reflectivedisplay apparatus according to claim 1, wherein said colored area is alight absorbing layer and includes a plane overlapping with said supportmember within a plane horizontal to said back substrate.
 9. Thereflective display apparatus according to claim 1, wherein said coloredarea is a light absorbing layer and provided on one side of the displayarea of said display apparatus.
 10. The reflective display apparatusaccording to claim 1, wherein said colored area is a light absorbinglayer and placed between said first electrode and second electrode, andsaid back substrate.
 11. The reflective display apparatus according toclaim 1, wherein said reflecting means is said plurality of types ofcharged particles.
 12. The reflective display apparatus according toclaim 1, wherein said reflecting means is a light reflecting layerprovided on said back substrate.
 13. The reflective display apparatusaccording to claim 12, wherein said light reflecting layer includes atleast one of said first electrode or second electrode.
 14. Thereflective display apparatus according to claim 12, wherein the surfaceof said light reflecting layer is provided with a concavo-convexostructure.
 15. An electrophoresis display apparatus comprising: a firstsubstrate and second substrate arranged with a predetermined gap inbetween; an insulating liquid and a plurality of charged particlesenclosed in the gap between these substrates; a first electrode placedalong said first substrate over a relatively wide area of a pixel; and asecond electrode between which and said first electrode a voltage isapplied, said electrophoresis display apparatus carrying out a displayby applying a voltage to these electrodes and moving said chargedparticles, wherein said charged particles are colored in a first color,at least a portion of the area where said first electrode is placed inwhich the density of said charged particles cannot be kept high iscolored in substantially the same color as said first color, at least aportion of the area where said first electrode is placed in which thedensity of said charged particles can be kept high is colored in asecond color, when said charged particles are placed so as to cover saidfirst electrode, said first color is visually recognized, and when saidcharged particles are attracted to said second electrode andaccumulated, said second color is visually recognized.